1. Field of the Invention
The present invention relates to a liquid crystal display of superior quality which has fewer components and a simpler manufacturing process than the conventional LCD, and particularly, to a frame of the LCD fastening and determining positions of a back light unit and a liquid crystal panel.
2. Discussion of the Related Art
Liquid crystal displays (LCDs) are very widely used in environments such as offices, schools, libraries and homes. The LCD has easy portability due to its light weight and small size. The LCD is widely used as a display device in personal computers, audio visual (AV) systems, portable computers, game machines, and simulators. Active research has focused on the development of an LCD with a simplified manufacturing process, reduced number of components, reduced manufacturing time, and thinner design, thereby reducing prices.
In a conventional LCD, a back light and a liquid crystal display panel are fixed to a frame. The back light unit includes a light reflecting sheet attached to one face of a light guide, a diffusing sheet and a light condensing sheet attached to the other face of the light guide, and a light reflector having a lamp therein and partially enclosing one side of the light guide. The liquid crystal display panel includes two glass substrates, switching elements formed on the inner surface of one of the two glass substrates, liquid crystal injected between the two glass substrates and polarizing plates attached on each outer surface of the two substrates.
The conventional LCD will now be explained with reference to FIGS. 1-7.
As shown in FIG. 1, a light guide 4 and a light reflector 3 are fixed to a frame 1. On the light guide 4 and the light reflector 3, the position of a liquid crystal display panel 2 is determined by the frame 1. The light guide 4 is fixed by a screw 8. A wire 5 received from a lamp (not shown) is provided in the light reflector 3. A position determiner 6 is also provided for the liquid crystal display panel 2.
The conventional LCD is depicted in FIGS. 2, 3, and 4 which are cross-sectional views taken along lines II--II, III--III, and IV--IV, respectively.
FIG. 2 shows a light diffusing sheet 10 and a light condensing sheet 11 which are layered and attached to one surface of the light guide 4. A light reflecting sheet 9 is attached onto the other surface of the light guide 4. A standing side 16 of the frame 1 determines the location of the light guide 4 with an inner portion 50, and a screw 8 fixes the light guide 4 to the frame 1.
FIG. 3 shows the light diffusing sheet 10 and the light condensing sheet 11 layered on one surface of the light guide 4. The light reflecting sheet 9 is attached to the other surface of the light guide 4. A U-shaped light reflector 3, having a lamp 30 therein, sandwiches the edge of the light guide 4. The position of the light guide 4 is determined by the lower inner portion 50 of the standing side 16 of the frame 1. A liquid crystal display panel 2 which includes two substrates 12 and 13 and polarizing plates 88 attached to the outer surfaces of each substrate is located next to a upper inner portion 60 of the standing side 16. The standing side 16 of the frame 1 has an inner portion resembling a staircase, of which first step 50 determines the position of the light guide 4 and the second step 60 determines the position the liquid crystal display panel 2.
In FIG. 4, the light diffusing sheet 10 and the light condensing sheet 11 are layered on one surface of the light guide 4. The light reflecting sheet 9 is attached to the opposite surface of the light guide 4. The position of the light guide 4 is determined by the first step 50 of the standing side 16 of the frame 1. The position of a liquid crystal display panel 2 which includes two substrates 12 and 13 and polarizing plates 88 attached to the outer surfaces of each substrate is determined by the second step 60 of the standing side 16.
FIG. 5 shows a modification of the structure from FIG. 3. Here, the light diffusing sheet and the light condensing sheet 11 are layered on one surface of the light guide 4. The light reflecting sheet 9 is attached to the opposite surface of the light guide 4. A U-shaped light reflector 3, having the lamp 30 therein, partially encloses the light guide 4 and the light reflecting sheet 9. The position of the light guide 4 is determined by the standing side 16 of the frame 1. A separate position determiner 6' for the liquid crystal display panel 2 is fixed on the standing side 16 with adhesives or a pin 136. The light reflector 3 enclosing the light guide 4 is fixed to the frame 1 by placing it into a gap between the bottom the frame 1 and the separate position determiner 6' for the liquid crystal display panel 2. A inner portion 60 of the position determiner 6' determines the position of the liquid crystal display panel 2. A wire 5 coming from the lamp 30 is hung on a groove 90 of the position determiner 6'.
As shown in FIGS. 3 and 4, the positions of the light guide 4 and the liquid crystal display panel 2 in a conventional LCD are determined by only the standing side 16 of the frame having a stepped wall. As a result, they are not securely fixed and easily moved by even a minor impact. Therefore, they are easily damaged.
In order to solve this problem, a screw 8 is used to fix the light guide 4 as shown in FIG. 1. This, however, requires an additional area for the screw in the frame 1 and the light guide 4, making the design structure thereof complicated, and resulting in the deterioration of uniform illumination. As a result of the accommodations required for the screw, the manufacturing process becomes lengthier and manufacturing costs are thereby increased.
Referring to FIG. 5 showing an improvement of FIG. 3, a separate position determiner 6' for the liquid crystal display panel 2 is created and fixed on the standing side 16 of the frame 1 with adhesives or a pin 136. However, other problems still exist in that the separate position determiner 6' for the liquid crystal display panel 2 is easily detached from the standing side 16 by a minor impact during the manufacturing process, resulting in the scattering and damaging of components. As a result thereof, the quality of the LCD is diminished.
As described above, the creation of the separate position determiner 6' requires an additional manufacturing step, thereby increasing in manufacturing costs.
A further improved frame in the conventional LCD is disclosed in Japanese Patent Publication No. 5-66390. A supporter is created apart from the frame and fixed to the edge of the frame by a projecting portion of the frame. A back light unit and a liquid crystal display panel fix in place. A more detailed description will now be provided with reference to FIGS. 6 and 7.
As shown in FIGS. 6 and 7, the projecting part 111 of the frame 1 is locked with the supporter 81 at the edge of the frame 1. The position of a lamp 30 connected to the light guide is determined by a pair of projecting portions 61a and 61b projecting from the supporter 81 and a pair of projecting parts 42 projecting from the lamp 30. A space is formed between the projecting portion 61a and the side wall of the frame 1, in which a wire 5 from the lamp 30 is hung.
The supporter 81 has a stair-like profile of which the first step 59 determines the position of the light guide and the second step 56 determines the position of the liquid crystal display panel, respectively.
The supporter 81 and the projecting part 111 which fix and determine the position of the back light unit and the liquid crystal display panel, become easily detached from each other during the manufacturing process, resulting in the unstable positioning of the back light unit and liquid crystal display panel.
In addition, an additional step for locking the supporter 81 to the frame 1 is required, thereby increasing manufacturing time and cost.